The United States has expanded its air strikes against Islamic State (IS) in Afghanistan since President Barack Obama granted commanders broader authority to target the group there, a U.S. military spokesman said on February 11.

IS is a relatively new force in Afghanistan, where the militant group has challenged the Taliban. Concerned about the group’s increasingly global reach, Obama granted the U.S. military broad authority to strike IS there in January.

“The change in authorities has given us additional flexibility” and “significantly increased” the number of strikes, said military spokesman Brigadier General Wilson Shoffner.

Officials said 20 strikes have been launched in the eastern part of the country in the last three weeks. They credited the strikes, in combination with Afghan and NATO joint operations, with containing IS in eastern Afghanistan.

Shoffner said IS has some 1,000 to 3,000 members in eastern Afghanistan and was attempting to establish a base of operations in Nangarhar. NATO aircraft struck an IS radio station there this month.

While IS has been an increasing problem in eastern Afghanistan, U.S. and coalition efforts have been more focused on the south, where the Taliban has been launching attacks since October.